Sodium metabisulfite CAS:7681-57-4

  • Product Name:Sodium metabisulfite
  • CAS:7681-57-4
  • Molecular formula:2Na.O5S2
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Sodium metabisulfite CAS:7681-57-4

Sodium metabisulfite CAS:7681-57-4 Basic information

Product Name: Sodium metabisulfite
Synonyms: SODIUM META-BISULFITE GRAN;Sodiummetabisulfite,ACS,97%min;Sodium metabisulfite, anhydrous, extra pure, 97%;Sodium metabisulfite, for analysis ACS, 97+%;SODIUM META BISULFITE REAGENT (ACS);sodium metabisulfite, acs;SODIUMMETABISULFITE,ANHYDROUS,GRANULAR,RE
CAS: 7681-57-4
MF: 2Na.O5S2
MW: 190.11
EINECS: 231-673-0
Product Categories: INORGANIC & ORGANIC CHEMICALS;Inorganics;inhibitor and freshen agent
Mol File: 7681-57-4.mol

Sodium metabisulfite CAS:7681-57-4 Chemical Properties

density: 1.48
Melting point: 150 °C
form: Powder/Solid
storage temp.: Store at RT.
Water Solubility: 540 g/L (20 ºC)
solubility: 540 g/L (20°C)
Merck: 14,8638
Stability: Stable. Incompatible with strong oxidizing agents, strong acids. Contact with strong acids releases a poisonous gas. May be moisture and air sensitive.
Sensitive: Air & Moisture Sensitive
Specific Gravity: 1.48
Odor: Sulphorous
CAS DataBase Reference: 7681-57-4(CAS DataBase Reference)
EPA Substance Registry System: Sodium metabisulfite (7681-57-4)





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White with yellowish crystalline powder



Sodium metabisulfite Usage And Synthesis
DescriptionSodium metabisulfite (chemical formula: Na2S2O5) appears as a white crystalline or powder solid with a slight sulfur odor. It is toxic upon inhalation and can strongly irritate skin and tissue. It can be decomposed to release toxic oxide fumes of sulfur and sodium upon high temperature. It can be mixed with water to form a corrosive acid. It is generally used as disinfectant, antioxidant, and preservative agent as well as a laboratory reagent. As a kind of food additive, it can be used as a preservative and antioxidant in food. It can also be applied to the wine and beer making. Moreover, it can be used to sanitize the equipment of homebrew and winemaking as a cleaning agent. It also have various kinds of other applications, e.g. being applied to photography, as an excipients in some tablets, for water treatment, as a source of SO2 in wine, as a bactericide and as a bleaching reagent as well as reducing agent. It can be manufactured through the evaporation of a sodium bisulfite which has been saturated with sulfur dioxide. It should be warned that sodium metabisulfite has certain acute effects on the respiratory system, eyes and skin. In severe case, it can cause breathing difficulty and even pulmonary damage which finally leads to death. Therefore, effective protective measures and attention should be taken during the operation.
sodium metabisulfite powder
sodium metabisulfite powder
UsesSodium metabisulfite (SMBS, Sodium disulfite) is a white, granular solid sodium salt. an inorganic compound made up of sodium, sulfur, and oxygen, and used in many industries:
  1. in the pulp and paper industry, in the photographic industry and in the various other industries as a bleach or dechlorinator.

  2. Food Grade sodium metabisulfite may be used as a food preservative. It is also commonly added to various food products and wines as a preservative.

  3. Sodium metabisulfite can also be used in the manufacture of other chemicals, Used in production of cleaning agents, detergents, and soaps.

  4. It also acts as a corrosion inhibitor in oil and gas industry, as a bleaching agent in the production of coconut cream, as the source of sulfur dioxide and in the destruction of cyanide in commercial gold cyanidation processes.

  5. Gold mining industry: It is utilized in the precipitation of gold from auric acid as well as in the waste water treatment to remove hexavaent chromium as trivalent chromium by precipitation after reduction.

  6. Preservative in photo developer solutions, it is used in photography.

  7. Oxygen scavenge:it plays as an oxygen scavenger to eliminate the dissolved oxygen in wastewater and in pipes.

  8. Sodium metabisulfite may be used as an initiator during the cross-linking polymerization of polybutadiene in the cores of the vesicle membranes.

  9. It may be added as an antioxidant during the preparation of stock solutions of 6-hydroxydopamine in various studies.

  10. Dechlorination in municipal wastewater, pulp & paper, power, and textile water treatment plants.

Preparationmanufactures sodium metabisulfite by reacting sulfur dioxide with sodium carbonate (soda ash), purifying and drying to form crystals or powder.
Na2CO3 + 2SO2→Na2S2O5 + CO2
Product Specification
Sodium Metabisulfite, wt%
98.7% min.
Assay as SO2
66.5 min.
Insolubles, wt%
≤ 0.005
Chloride, wt%
≤ 0.05
Thiosulfate, wt%
≤ 0.05
Arsenic, ppm
≤ 1.0
Heavy metals, ppm
≤ 10.0
Iron as (Fe), ppm
≤ 2.0
Selenium, ppm
≤ 5.0
Lead as (Pb), ppm
≤ 2.0
Health HazardSodium metabisulphite is currently listed in Annex III Part B of Directive 95/2/EC as an authorised food additive. As such food labelling is required where sulphite residues exceed 10 mg/kg (ppm). This is labelled E223 with maximum permitted residues in crustacean products set at 150 mg/kg. However it is now accepted that sulphites, when present in foodstuffs, can cause allergic reactions in vulnerable persons and can constitute a danger to health (Collins-Williams, 1983). Metabisulphite is regarded as one causative agent of asthma attacks (Gunnison & Jacobsen, 1987). In accordance with this, EU Directive 2003/89/EC will make allergen labelling a requirement for all food stuffs produced in the European Community, which have been treated with sodium metabisulphite.
Sodium metabisulfite typically found in consumer products should pose little a risk of symptoms due to skin or inhalation exposure since sodium metabisulfite is used in very low concentrations. Sodium metabisulfite can produce the following adverse health affects:
  1. Contact - Skin exposures can cause symptoms ranging from minor skin irritation or itching to redness and swelling. Eye exposure to sodium metabisulfite may result in redness, tearing or moderate eye irritation.

  2. Inhalation - The inhalation of sodium metabisulfite dusts can cause nose and throat irritation or coughing. Repeated or prolonged exposures may cause sore throat or nosebleeds. Inhalation may also cause severe respiratory reactions and aggravate asthma or other breathing diseases.

  3. Ingestion - The ingestion of sodium metabisulfite may cause irritation of the mouth and throat, nausea, vomiting and diarrhea.

  4. Other Effects - The International Agency for Research on Cancer (IARC) has not classified sodium metabisulfite as a carcinogen (cancer causing).

Chemical Propertieswhite crystalline powder with a sulfur smell
Chemical PropertiesSodium metabisulfite is a white crystalline powder. Sulfur dioxide odor. It may be considered the anhydride of 2 molecules of sodium disulfite.
Chemical PropertiesSodium metabisulfite occurs as colorless, prismatic crystals or as a white to creamy-white crystalline powder that has the odor of sulfur dioxide and an acidic, saline taste. Sodium metabisulfite crystallizes from cold water as a hydrate containing seven water molecules.
UsesPharmaceutic aid (antioxidant).
Usessodium metabisulfite is an anti-oxidant and reducing agent.
UsesSodium Metabisulfite is a preservative and antioxidant that exists as crystals or powder having a sulfur dioxide odor. it is readily solu- ble in water. it is used in dried fruits to preserve flavor, color, and to inhibit undesirable microorganism growth. it prevents “black spots” due to oxidative deterioration in shrimp. it is used in maraschino cherries. it is found in lemon drinks as a preservative. see sulfur dioxide.
DefinitionChEBI: An inorganic sodium salt composed of sodium and disulfite ions in a 2:1 ratio.
Production MethodsSodium metabisulfite is prepared by saturating a solution of sodium hydroxide with sulfur dioxide and allowing crystallization to occur; hydrogen is passed through the solution to exclude air. Sodium metabisulfite may also be prepared by saturating a solution of sodium carbonate with sulfur dioxide and allowing crystallization to occur, or by thermally dehydrating sodium bisulfite.
HazardToxic by inhalation. Upper respiratory tract irritant. Questionable carcinogen.
Health HazardSodium metabisulfite may cause bronchospasm, oculonasal symptoms, and urticaria in sulfite-sensitive individuals; irritation of mucous membranes may occur from inhalation of the dust.
Pharmaceutical ApplicationsSodium metabisulfite is used as an antioxidant in oral, parenteral, and topical pharmaceutical formulations, at concentrations of 0.01–1.0% w/v, and at a concentration of approximately 27% w/v in intramuscular injection preparations. Primarily, sodium metabisulfite is used in acidic preparations; for alkaline preparations, sodium sulfite is usually preferred. Sodium metabisulfite also has some antimicrobial activity, which is greatest at acid pH, and may be used as a preservative in oral preparations such as syrups.
In the food industry and in wine production, sodium metabisulfite is similarly used as an antioxidant, antimicrobial preservative, and antibrowning agent. However, at concentrations above about 550 ppm it imparts a noticeable flavor to preparations. Sodium metabisulfite usually contains small amounts of sodium sulfite and sodium sulfate.
Contact allergensThis agent is frequently used as a preservative in pharmaceutical products, in the bread-making industry as an antioxidant, and it can induce contact dermatitis. It can be used as a reducing agent in photography and caused dermatitis in a photographic technician, probably acting as an aggravating irritative factor. Sodium metabisulfite contains a certain amount of sodium sulfite and sodium sulfate.
Safety ProfileAn inhalation hazard. Poison by intravenous route. Moderately toxic by parenteral route. Experimental reproductive effects. Mutation data reported. When heated to decomposition it emits toxic fumes of SOx and Na2O.
SafetySodium metabisulfite is widely used as an antioxidant in oral, topical, and parenteral pharmaceutical formulations; it is also widely used in food products.
Although it is extensively used in a variety of preparations, sodium metabisulfite and other sulfites have been associated with a number of severe to fatal adverse reactions. These are usually hypersensitivity-type reactions and include bronchospasm and anaphylaxis. Allergy to sulfite antioxidants is estimated to occur in 5–10% of asthmatics, although adverse reactions may also occur in nonasthmatics with no history of allergy.
Following oral ingestion, sodium metabisulfite is oxidized to sulfate and is excreted in urine. Ingestion may result in gastric irritation, owing to the liberation of sulfurous acid, while ingestion of large amounts of sodium metabisulfite can cause colic, diarrhea, circulatory disturbances, CNS depression, and death.
In Europe, the acceptable daily intake of sodium metabisulfite and other sulfites used in foodstuffs has been set at up to 3.5 mg/kg body-weight, calculated as sulfur dioxide (SO2). The WHO has similarly also set an acceptable daily intake of sodium metabisulfite, and other sulfites, at up to 7.0 mg/kg body-weight, calculated as sulfur dioxide (SO2).
LD50 (rat, IV): 0.12 g/kg
Potential ExposureSodium metabisulfite is used as an antioxidant in pharmaceutical preparations and as a preservative in foods. People with asthma have a greater chance of having an allergic reaction with this chemical. Individuals allergic to sodium bisulfite (a food preservative found in some wine, fresh shrimp; packaged foods; and restaurant salads and potatoes) may have a severe reaction when exposed to sodium metabisulfite.
CarcinogenicitySodium metabisulfite was genotoxic in mice in vivo as determined by chromosomal aberration, micronucleus, and sperm shape assays. It was not mutagenic in bacterial assays.
storageOn exposure to air and moisture, sodium metabisulfite is slowly oxidized to sodium sulfate with disintegration of the crystals. Addition of strong acids to the solid liberates sulfur dioxide.
In water, sodium metabisulfite is immediately converted to sodium (Na+) and bisulfite (HSO3-) ions. Aqueous sodium metabisulfite solutions also decompose in air, especially on heating. Solutions that are to be sterilized by autoclaving should be filled into containers in which the air has been replaced with an inert gas, such as nitrogen. The addition of dextrose to aqueous sodium metabisulfite solutions results in a decrease in the stability of the metabisulfite.
The bulk material should be stored in a well-closed container, protected from light, in a cool, dry place.
ShippingUN1759 Corrosive solids, n.o.s., Hazard class: 8; Labels: 8-Corrosive material, Technical Name required. UN2693 Bisulfites, inorganic, aqueous solutions, n.o.s., Hazard class: 8; Labels: 8-Corrosive material.
IncompatibilitiesA strong reducing agent. Keep away from oxidizers. Mixtures with water forms a strong corrosive. Contact with acids releases toxic fumes. Heat causes decomposition. Slowly oxidized to the sulfate on exposure to air and moisture. Attacks metals
IncompatibilitiesSodium metabisulfite reacts with sympathomimetics and other drugs that are ortho- or para-hydroxybenzyl alcohol derivatives to form sulfonic acid derivatives possessing little or no pharmacological activity. The most important drugs subject to this inactivation are epinephrine (adrenaline) and its derivatives. In addition, sodium metabisulfite is incompatible with chloramphenicol owing to a more complex reaction; it also inactivates cisplatin in solution.
It is incompatible with phenylmercuric acetate when autoclaved in eye drop preparations.
Sodium metabisulfite may react with the rubber caps of multidose vials, which should therefore be pretreated with sodium metabisulfite solution.
Regulatory StatusGRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (epidural;inhalation; IM and IV injections; ophthalmic solutions; oral preparations; rectal, topical, and vaginal preparations). Included in nonparenteral and parenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.

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